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PURPOSE: To compare the clinical and tomographic properties of adult patients with keratoconus treated with accelerated corneal cross-linking (A-CXL) versus accelerated contact lens–assisted corneal cross-linking (A-CACXL). METHODS: Patients who underwent A-CXL and A-CACXL due to progressive keratoconus were enrolled from January 2015 to January 2018 in this retrospective case–control study. The treatment group (minimum corneal thickness of less than 400 µm after epithelium removal; 30 patients, 30 eyes) was treated with A-CACXL; the control group (minimum corneal thickness of 400 µm or greater, 32 patients, 32 eyes) was treated with A-CXL. Assessments occurred before treatment and 12 months postoperatively. Demographic, clinical, and tomographic data were obtained from outpatient clinic reports. RESULTS: Significant improvement in visual acuity was evident at 12-month follow-up for the control group in uncorrected distance visual acuity (0.62 ± 0.42 vs 0.43 ± 0.31 logMAR, P = .01) and the treatment group in corrected distance visual acuity (0.51 ± 0.30 vs 0.40 ± 0.49 logMAR, P = .03). Progression of keratoconus was halted at similar rates for both groups (76.7% treatment, 84.4% control, P = .21). Mean minimum corneal thickness showed minor but significant thinning at the 12-month follow-up visit compared to baseline (control group = 463 ± 31 vs 450 ± 35 µm, P > .01; treatment group = 398 ± 32 vs 388 ± 41 µm, P = .02). CONCLUSIONS: A-CACXL halted keratoconus progression in 76.7% of eyes and achieved regression in 33.3% of eyes, with rates comparable to A-CXL. Visual outcomes improved for both groups, with similar keratometry changes. A-CACXL is an effective and safe option for patients with keratoconus and thin corneas, with results similar to A-CXL treatment in patients with a minimum corneal thickness of 400 µm or greater. [ J Refract Surg . 2021;37(9):623–630.]

To determine the effect of the hormones estrogen and progesterone on the biomechanical properties of porcine corneas. Thirty fresh porcine corneas were acquired from an abattoir. The corneas were equally divided into three groups. Groups were incubated for 1 week in Eusol-C solution containing supra-physiologic concentrations of estrogen, progesterone, or control (no added hormone). After incubation, the central corneal thickness (CCT) of each cornea was measured using an electronic caliper, and then the corneas were cut into strips. The strips were then clamped in the pneumatic jaws of a computer-controlled biomaterial tester (Instron 4502, USA) and stretched at a constant rate of 1 mm/min until tissue rupture while constantly recording the stress and strain of the tissue. Stress–strain curves were plotted and Young’s modulus was calculated for each corneal strip. Average corneal thickness was 873.5 ± 143.1 μm for the control group, 928.0 ± 97.7 μm for the estrogen group, and 922.0 ± 116.7 μm for the progesterone group (data presented as mean ± SD). There was no statistically significant difference between the groups regarding the CCT (p = 0.89). The average Young’s modulus was 17.00 ± 3.46 MPa for the control group, 16.95 ± 6.83 MPa for the progesterone group, and 12.33 ± 3.24 MPa for the estrogen group. The difference between the control and estrogen groups was statistically significant (p = 0.018) while the difference between the control and progesterone groups was not (p = 0.72). Estrogen has a relaxing effect on the porcine cornea, resulting in reduced stiffness of the tissue. Progesterone has no significant effect on the biomechanical properties of porcine corneas. Estrogen and progesterone do not significantly affect CCT.

PURPOSE: To evaluate the safety and efficacy of accelerated contact lens–assisted cross-linking (A-CACXL) for patients with keratoconus and thin corneas. METHODS: This retrospective study included consecutive patients undergoing A-CACXL for progressive keratoconus from 2015 to 2017. Patients with a minimum corneal thickness of 400 µm or less after epithelium removal who underwent A-CACXL (9 mW/cm 2 for 10 minutes, using iso-osmolar 0.1% riboflavin solution and a 90-µm thick, daily disposable bandage soft contact lens) with a follow-up time of 12 months or more were included. The main outcome measures were uncorrected (UDVA) and corrected (CDVA) distance visual acuity and minimum corneal thickness at the last visit. Progression (increase) and flattening (decrease) were defined as a change of 1.00 diopters (D) or greater in maximum keratometry or 1.50 D or greater in mean keratometry. RESULTS: Overall, 24 eyes of 24 patients were included with a follow-up time of 18.2 ± 6.3 months and a mean minimum corneal thickness, after epithelial debridement, of 353.13 µm. There was a significant improvement in UDVA ( P = .009), maximum keratometry ( P = .03), anterior steep keratometry ( P = .04), anterior astigmatism ( P = .02), and posterior astigmatism ( P = .04) with no significant change in minimum corneal thickness ( P = .11). There was a significant improvement in UDVA (0.90 ± 0.63 to 0.64 ± 0.47 logMAR, P = .009), maximum keratometry (61.20 ± 6.30 to 59.90 ± 5.70 D, P = .03), anterior steep keratometry (55.10 ± 3.90 to 54.50 ± 4.10 D, P = .04), anterior astigmatism (5.50 ± 2.40 to 4.60 ± 2.10 D, P = .02), and posterior astigmatism (0.90 ± 0.40 to 0.80 ± 0.40 D, P = .04) with no significant change in minimum corneal thickness (from 399.8 ± 30.7 to 391.0 ± 43.8 μm, P = .11). Flattening occurred in 45.8% (n = 11) and progression in 20.8% (n = 5). There were no serious adverse events. Persistent clinically significant stromal haze occurred in one case and completely resolved by 6 months. There was no significant change in endothelial cell density ( P = .10). CONCLUSIONS: In patients with keratoconus and thin corneas, A-CACXL halted keratoconus progression in 80%, led to flattening in 45%, and significantly improved UDVA and keratometry values without any evidence of damage to the corneal endothelium or permanent adverse events. [ J Refract Surg. 2019;35(10):642–648.]

Introduction. Keratoconus is a progressive corneal disease commonly treated by collagen cross-linking (CXL). Accelerated protocols have recently become common. This study sought to compare the outcomes of accelerated and standard CXL in terms of visual acuity, keratometry, and tomographic parameters in pediatric population. Methods. We retrospectively reviewed the files of pediatric patients who underwent standard and accelerated CXL for keratoconus in our hospital, between October 2014 and March 2018. Changes in uncorrected distance visual acuity (UCDVA), best corrected distance visual acuity (BCDVA), tomographic keratometry parameters (Kmax, Ksteep, Kflat, Kmean), and endothelial density count (EDC) were assessed before and at 6 and 12 months following treatment. The analysis included intergroup and intragroup comparisons. Results. This study included 53 eyes (44 patients). Fourteen eyes were treated with standard CXL (S-CXL, 3 mW/cm2, 30 min), while 39 underwent accelerated CXL (A-CXL, 9 mW/cm2, 10 min). Intergroup comparison found insignificant differences between groups, with the exception of better results for UCDVA in the S-CXL group after 12 months ( P = 0.03). In this study, there was no significant difference between the two protocols postoperatively in BCDVA, Kmax, Kmean, pachymetry, or corneal astigmatism. Conclusion. A-CXL is as safe and effective as S-CXL for stabilizing progressive keratoconus in pediatric population. Larger-sample-size studies with a longer follow-up time are required. Considering the long-term results of 9 mW A-CXL and its safety and efficacy profile, it should be preferred to S-CXL for reducing treatment time and improving patients’ comfort.